Geared architecture with inducer for gas turbine engine

ABSTRACT

A gas turbine engine includes first and second shafts rotatable about a common axis. A first turbine section is supported on the first shaft. Second compressor and turbine sections are supported on the second shaft. The gas turbine engine includes a fan. A first compressor section is arranged in an axial flow relationship with the second compressor and the first and second turbines. A geared architecture operatively connects the first shaft and the fan. An inducer operative couples to the gear train.

BACKGROUND

This disclosure relates to a geared architecture for a gas turbineengine.

One type of geared turbofan engine includes a two-spool arrangement inwhich a low spool, which supports a low pressure turbine section, iscoupled to a fan via a planetary gear train. A high pressure spoolsupports a high pressure turbine section. Low and high pressurecompressor sections are respectively supported by the low and highspools.

The planetary gear train includes a planetary gear set surrounding andintermeshing with a centrally located sun gear that is connected to thelow spool. A ring gear circumscribes and intermeshes with the planetarygears. A fan shaft supports the fan. The fan shaft is connected toeither the planetary gears or the ring gear, and the other of theplanetary gears and ring gear is grounded to the engine staticstructure. This type of planetary gear arrangement can limit the designspeeds of and configuration of stages in the low and high pressureturbine sections.

SUMMARY

In one exemplary embodiment, a gas turbine engine includes first andsecond shafts rotatable about a common axis. A first turbine section issupported on the first shaft. Second compressor and turbine sections aresupported on the second shaft. The gas turbine engine includes a fan. Afirst compressor section is arranged in an axial flow relationship withthe second compressor and the first and second turbines. A gearedarchitecture operatively connects the first shaft and the fan. Aninducer operative couples to the gear train.

In a further embodiment of any of the above, the gas turbine engineincludes a bypass flow path and a core flow path. The first and secondcompressor and turbine sections are arranged in the core flow path, andthe fan extends into the bypass flow path. The inducer is arranged inthe core flow path outside of the bypass flow path and upstream from thefirst compressor section.

In a further embodiment of any of the above, first and second shaftsrespectively provide low and high spools. The first compressor andturbine sections are low pressure compressor and turbine sections. Thesecond compressor and turbine sections are high pressure compressor andturbine sections.

In a further embodiment of any of the above, the geared architectureincludes first and second gear trains. The first gear train is anepicyclic gear train, and the second gear train is configured to providea speed reduction.

In a further embodiment of any of the above, the inducer is coupled tothe first gear train. The epicyclic gear train is a differential geartrain that includes a sun gear. Planetary gears are arranged about andintermesh with the sun gear. A ring gear circumscribes, and intermesheswith the planetary gears.

In a further embodiment of any of the above, the inducer is rotationallyfixed relative to the ring gear.

In a further embodiment of any of the above, the inducer is rotationallyfixed relative to the star gear.

In a further embodiment of any of the above, the inducer is coupled tothe second gear train.

In a further embodiment of any of the above, the inducer is rotationallyfixed relative to the fan.

In a further embodiment of any of the above, the inducer is configuredto rotate at a different rotational speed than the first compressorsection.

In a further embodiment of any of the above, the inducer is configuredto rotate at a different rotational speed than the fan.

In a further embodiment of any of the above, the inducer is configuredto rotate at a different rotational speed than the fan.

In one exemplary embodiment, a gas turbine engine includes first andsecond shafts rotatable about a common axis. A first turbine section issupported on the first shaft. Second compressor and turbine sections aresupported on the second shaft. The gas turbine engine includes a fan. Afirst compressor section is arranged in an axial flow relationship withthe second compressor and the first and second turbines. A gearedarchitecture operatively connects the first shaft and the fan. Aninducer is operatively coupled to the gear train. The gas turbine engineincludes a bypass flow path and a core flow path. The first and secondcompressor and turbine sections are arranged in the core flow path, andthe fan extends into the bypass flow path. The inducer is arranged inthe core flow path outside of the bypass flow path and upstream from thefirst compressor section. First and second shafts respectively providelow and high spools. The first compressor and turbine sections are lowpressure compressor and turbine sections, and the second compressor andturbine sections are high pressure compressor and turbine sections. Thegeared architecture includes first and second gear trains. The firstgear train is an epicyclic gear train, and the second gear train isconfigured to provide a speed reduction.

In a further embodiment of any of the above, the inducer is coupled tothe first gear train. The epicyclic gear train is a differential geartrain that includes a sun gear. Planetary gears are arranged about andintermesh with the sun gear. A ring gear circumscribes and intermesheswith the planetary gears.

In a further embodiment of any of the above, the inducer is rotationallyfixed relative to the ring gear.

In a further embodiment of any of the above, the inducer is rotationallyfixed relative to the star gear.

In a further embodiment of any of the above, the inducer is coupled tothe second gear train.

In a further embodiment of any of the above, the inducer is rotationallyfixed relative to the fan.

In a further embodiment of any of the above, the inducer is configuredto rotate at a different rotational speed than the first compressorsection.

In a further embodiment of any of the above, the inducer is configuredto rotate at a different rotational speed than the fan.

In a further embodiment of any of the above, the inducer is configuredto rotate at a different rotational speed than the fan.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be further understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 schematically illustrates a gas turbine engine embodiment.

FIG. 2 is a schematic view of a geared architecture embodiment for theengine shown in FIG. 1.

FIG. 3 is a schematic view of another geared architecture embodiment.

FIG. 4 is a schematic view of a geared architecture embodiment with aninducer.

FIG. 5 is a schematic view of yet another geared architectureembodiment.

FIG. 6 is a schematic view of another geared architecture embodimentwith an inducer.

FIG. 7 is a schematic view of yet another geared architecture embodimentwith an inducer.

FIG. 8 is a schematic view of still another geared architectureembodiment with an inducer.

FIG. 9A is a schematic view of an epicyclic gear train having a firstexample geometry ratio.

FIG. 9B is a schematic view of an epicyclic gear train having a secondexample geometry ratio.

FIG. 9C is a schematic view of an epicyclic gear train having a thirdexample geometry ratio.

FIG. 10 is a nomograph depicting the interrelationship of speeds ofepicyclic gear train components for a given geometry ratio.

FIG. 11A is a schematic view of an epicyclic gear train having the firstgeometry ratio with a carrier rotating in the opposite direction to thatshown in FIG. 9A.

FIG. 11B is a schematic view of an epicyclic gear train having thesecond geometry ratio with a carrier rotating in the opposite directionto that shown in FIG. 9B.

FIG. 11C is a schematic view of an epicyclic gear train having the thirdgeometry ratio with a carrier rotating in the opposite direction to thatshown in FIG. 9C.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gasturbine engine 20 is disclosed herein as a two-spool turbofan thatgenerally incorporates a fan section 22, a compressor section 24, acombustor section 26 and a turbine section 28. Alternative engines mightinclude an augmentor section (not shown) among other systems orfeatures. The fan section 22 drives air along a bypass flowpath B whilethe compressor section 24 drives air along a core flowpath C forcompression and communication into the combustor section 26 thenexpansion through the turbine section 28. Although depicted as aturbofan gas turbine engine in the disclosed non-limiting embodiment, itshould be understood that the concepts described herein are not limitedto use with turbofans as the teachings may be applied to other types ofturbine engines including three-spool architectures.

The engine 20 generally includes a low speed spool 30 and a high speedspool 32 mounted for rotation about an engine central longitudinal axisA relative to an engine static structure 36 via several bearing systems38. It should be understood that various bearing systems 38 at variouslocations may alternatively or additionally be provided.

The low speed spool 30 generally includes an inner shaft 40 thatinterconnects a fan 42, a low pressure (or first) compressor section 44and a low pressure (or first) turbine section 46. The inner shaft 40 isconnected to the fan 42 through a geared architecture 48 to drive thefan 42 at a lower speed than the low speed spool 30. The high speedspool 32 includes an outer shaft 50 that interconnects a high pressure(or second) compressor section 52 and high pressure (or second) turbinesection 54. A combustor 56 is arranged between the high pressurecompressor 52 and the high pressure turbine 54. A mid-turbine frame 57of the engine static structure 36 is arranged generally between the highpressure turbine 54 and the low pressure turbine 46. The mid-turbineframe 57 supports one or more bearing systems 38 in the turbine section28. The inner shaft 40 and the outer shaft 50 are concentric and rotatevia bearing systems 38 about the engine central longitudinal axis A,which is collinear with their longitudinal axes. As used herein, a “highpressure” compressor or turbine experiences a higher pressure than acorresponding “low pressure” compressor or turbine.

The core airflow C is compressed by the low pressure compressor 44 thenthe high pressure compressor 52, mixed and burned with fuel in thecombustor 56, then expanded over the high pressure turbine 54 and lowpressure turbine 46. The mid-turbine frame 57 includes airfoils 59 whichare in the core airflow path. The turbines 46, 54 rotationally drive therespective low speed spool 30 and high speed spool 32 in response to theexpansion.

The engine 20 in one example is a high-bypass geared aircraft engine. Ina further example, the engine 20 bypass ratio is greater than about six(6), with an example embodiment being greater than ten (10), the gearedarchitecture 48 is an epicyclic gear train, such as a star gear systemor other gear system, with a gear reduction ratio of greater than about2.3 and the low pressure turbine 46 has a pressure ratio that is greaterthan about 5. In one disclosed embodiment, the engine 20 bypass ratio isgreater than about ten (10:1), the fan diameter is significantly largerthan that of the low pressure compressor 44, and the low pressureturbine 46 has a pressure ratio that is greater than about 5:1. Lowpressure turbine 46 pressure ratio is pressure measured prior to inletof low pressure turbine 46 as related to the pressure at the outlet ofthe low pressure turbine 46 prior to an exhaust nozzle. It should beunderstood, however, that the above parameters are only exemplary of oneembodiment of a geared architecture engine and that the presentinvention is applicable to other gas turbine engines including directdrive turbofans.

A significant amount of thrust is provided by the bypass flow B due tothe high bypass ratio. The fan section 22 of the engine 20 is designedfor a particular flight condition—typically cruise at about 0.8 Mach andabout 35,000 feet. The flight condition of 0.8 Mach and 35,000 ft, withthe engine at its best fuel consumption—also known as “bucket cruiseThrust Specific Fuel Consumption (‘TSFC’)”—is the industry standardparameter of lbm of fuel being burned per hour divided by lbf of thrustthe engine produces at that minimum point. “Fan pressure ratio” is thepressure ratio across the fan blade alone, without a Fan Exit Guide Vane(“FEGV”) system. The low fan pressure ratio as disclosed hereinaccording to one non-limiting embodiment is less than about 1.45. “Lowcorrected fan tip speed” is the actual fan tip speed in ft/sec dividedby an industry standard temperature correction of [(Tram degR)/518.7)^0.5]. The “Low corrected fan tip speed” as disclosed hereinaccording to one non-limiting embodiment is less than about 1150ft/second.

An example geared architecture 48 for the engine 20 is shown in FIG. 2.Generally, the engine static structure 36 supports the inner and outershafts 40, 50 for rotation about the axis A. The outer shaft 50 supportsthe high pressure compressor section 52 and the high pressure turbinesection 54, which is arranged upstream from the mid turbine frame 59.

The inner shaft 40 is coupled to the geared architecture 48, which is anepicyclic gear train 60 configured in a differential arrangement. Thegear train 60 includes planetary gears 64 supported by a carrier 62,which is connected to the inner shaft 40 that supports the low pressureturbine 46. A sun gear 66 is centrally arranged relative to andintermeshes with the planetary gears 64. A ring gear 70 circumscribesand intermeshes with the planetary gears 64. In the example, a fan shaft72, which is connected to the fan 42, is rotationally fixed relative tothe ring gear 70. The low pressure compressor 44 is supported by a lowpressure compressor rotor 68, which is connected to the sun gear 66 inthe example.

The carrier 62 is rotationally driven by the low pressure turbine 46through the inner shaft 40. The planetary gears 64 provide thedifferential input to the fan shaft 72 and low pressure compressor rotor68 based upon the geometry ratio, which is discussed in detail inconnection with FIGS. 9A-10.

Another example geared architecture 148 for the engine 120 is shown inFIG. 3. The engine static structure 136 supports the inner and outershafts 140, 150 for rotation about the axis A. The outer shaft 150supports the high pressure compressor section 152 and the high pressureturbine section 154, which is arranged upstream from the mid turbineframe 159.

The inner shaft 140 is coupled to the geared architecture 148, which isan epicyclic gear train 160 configured in a differential arrangement.The gear train 160 includes planetary gears 164 supported by a carrier162, which is connected to the inner shaft 140 that supports the lowpressure turbine 146. A sun gear 166 is centrally arranged relative toand intermeshes with the planetary gears 164. A ring gear 170circumscribes and intermeshes with the planetary gears 164. In theexample, a fan shaft 172, which is connected to the fan 142, isrotationally fixed relative to the ring gear 170. The low pressurecompressor 144 is supported by a low pressure compressor rotor 168,which is connected to the sun gear 166 in the example.

The carrier 162 is rotationally driven by the low pressure turbine 146through the inner shaft 140. The planetary gears 164 provide thedifferential input to the fan shaft 172 and low pressure compressorrotor 168 based upon the geometry ratio. The geared architecture 148includes an additional speed change device 74 interconnecting the innershaft 140 and the gear train 160. Higher low pressure turbine sectionrotational speeds are attainable with the additional speed change device74, enabling the use of fewer turbine stages in the low pressure turbinesection. The speed change device 74 may be a geared arrangement and/or ahydraulic arrangement for reducing the rotational speed from the lowpressure turbine section 146 to the fan 142 and low pressure compressorsection 144.

Another example geared architecture 248 for the engine 220 is shown inFIG. 4. The engine static structure 236 supports the inner and outershafts 240, 250 for rotation about the axis A. The outer shaft 250supports the high pressure compressor section 252 and the high pressureturbine section 254, which is arranged upstream from the mid turbineframe 259.

The inner shaft 240 is coupled to the geared architecture 248, which isan epicyclic gear train 260 configured in a differential arrangement.The gear train 260 includes planetary gears 264 supported by a carrier262, which is connected to the inner shaft 240 that supports the lowpressure turbine 246. A sun gear 266 is centrally arranged relative toand intermeshes with the planetary gears 264. A ring gear 270circumscribes and intermeshes with the planetary gears 264. In theexample, a fan shaft 272, which is connected to the fan 242, isrotationally fixed relative to the ring gear 270. The low pressurecompressor 244 is supported by a low pressure compressor rotor 268,which is connected to the sun gear 266 in the example.

The carrier 262 is rotationally driven by the low pressure turbine 246through the inner shaft 240. The planetary gears 264 provide thedifferential input to the fan shaft 272 and low pressure compressorrotor 268 based upon the geometry ratio. The geared architecture 248includes an additional speed change device 274 interconnecting the innershaft 240 and the gear train 260.

An inducer 76 is fixed for rotation relative to the ring gear 270. Theinducer 76 is arranged in the core flow path C to provide some initialcompression to the air before entering the low pressure compressorsection 244. The inducer 76 rotates at the same rotational speed as thefan 242 and provides some additional thrust, which is useful in hotweather, for example, where engine thrust is reduced.

Another example geared architecture 348 for the engine 320 is shown inFIG. 5. The engine static structure 336 supports the inner and outershafts 340, 350 for rotation about the axis A. The outer shaft 350supports the high pressure compressor section 352 and the high pressureturbine section 354, which is arranged upstream from the mid turbineframe 359.

The inner shaft 340 is coupled to the geared architecture 348, which isan epicyclic gear train 360 configured in a differential arrangement.The gear train 360 includes planetary gears 364 supported by a carrier362, which is connected to the inner shaft 340 that supports the lowpressure turbine 346. A sun gear 366 is centrally arranged relative toand intermeshes with the planetary gears 364. A ring gear 370circumscribes and intermeshes with the planetary gears 364. In theexample, a fan shaft 372 is connected to the fan 342. The low pressurecompressor 344 is supported by a low pressure compressor rotor 368,which is rotationally fixed relative to the ring gear 370 in theexample.

The carrier 362 is rotationally driven by the low pressure turbine 346through the inner shaft 340. The planetary gears 364 provide thedifferential input to the fan shaft 372 and low pressure compressorrotor 368 based upon the geometry ratio. The geared architecture 348includes an additional speed change device 374 interconnecting the innershaft 340 and the gear train 360. The speed change device 374 receivesrotational input from the sun gear 366 and couples the fan shaft 372 tothe gear train 360, which enables slower fan speeds.

Another example geared architecture 448 for the engine 420 is shown inFIG. 6. The engine static structure 436 supports the inner and outershafts 440, 450 for rotation about the axis A. The outer shaft 450supports the high pressure compressor section 452 and the high pressureturbine section 454, which is arranged upstream from the mid turbineframe 459.

The inner shaft 440 is coupled to the geared architecture 448, which isan epicyclic gear train 460 configured in a differential arrangement.The gear train 460 includes planetary gears 464 supported by a carrier462, which is connected to the inner shaft 440 that supports the lowpressure turbine 446. A sun gear 466 is centrally arranged relative toand intermeshes with the planetary gears 464. A ring gear 470circumscribes and intermeshes with the planetary gears 464. In theexample, a fan shaft 472 is connected to the fan 442. The low pressurecompressor 444 is supported by a low pressure compressor rotor 468,which is rotationally fixed relative to the ring gear 470 in theexample.

The carrier 462 is rotationally driven by the low pressure compressor446 through the inner shaft 440. The planetary gears 464 provide thedifferential input to the fan shaft 472 and low pressure compressorrotor 468 based upon the geometry ratio. The geared architecture 448includes an additional speed change device 474 interconnecting the innershaft 440 and the gear train 460. The speed change device 474 receivesrotational input from the sun gear 466 and couples the fan shaft 472 tothe gear train 460, which enables slower fan speeds.

The inducer 476 is fixed for rotation relative to the fan shaft 472. Theinducer 476 is arranged in the core flow path C to provide some initialcompression to the air before entering the low pressure compressorsection 444. The inducer 476 rotates at the same rotational speed as thefan 442.

Another example geared architecture 548 for the engine 520 is shown inFIG. 7. The engine static structure 536 supports the inner and outershafts 540, 550 for rotation about the axis A. The outer shaft 550supports the high pressure compressor section 552 and the high pressureturbine section 554, which is arranged upstream from the mid turbineframe 559.

The inner shaft 540 is coupled to the geared architecture 548, which isan epicyclic gear train 560 configured in a differential arrangement.The gear train 560 includes planetary gears 564 supported by a carrier562, which is connected to the inner shaft 540 that supports the lowpressure turbine 546. A sun gear 566 is centrally arranged relative toand intermeshes with the planetary gears 564. A ring gear 570circumscribes and intermeshes with the planetary gears 564. In theexample, a fan shaft 572 is connected to the fan 542. The low pressurecompressor 544 is supported by a low pressure compressor rotor 568,which is rotationally fixed relative to the ring gear 570 in theexample.

The carrier 562 is rotationally driven by the low pressure turbine 546through the inner shaft 540. The planetary gears 564 provide thedifferential input to the fan shaft 572 and low, pressure compressorrotor 568 based upon the geometry ratio. The geared architecture 548includes an additional speed change device 574 interconnecting the innershaft 540 and the gear train 560. The speed change device 574 receivesrotational input from the sun gear 566 and couples the fan shaft 572 tothe gear train 560, which enables slower fan speeds.

The inducer 576 is fixed for rotation relative to the fan shaft 572. Theinducer 576 is arranged in the core flow path C to provide some initialcompression to the air before entering the low pressure compressorsection 544. In one example, the sun gear 566 rotates at the same speedas one of the fan shaft 572 and the inducer 576, and the other of thefan shaft 572 and the inducer 576 rotate at a different speed than thesun gear 566. In another example, the inducer 576, sun gear 566 and fanshaft 572 rotate at different rotational speeds than one another throughthe speed change device 574, which is another epicyclic gear train, forexample.

Another example geared architecture 648 for the engine 620 is shown inFIG. 8. The engine static structure 636 supports the inner and outershafts 640, 650 for rotation about the axis A. The outer shaft 650supports the high pressure compressor section 652 and the high pressureturbine section 654, which is arranged upstream from the mid turbineframe 659.

The inner shaft 640 is coupled to the geared architecture 648, which isan epicyclic gear train 660 configured in a differential arrangement.The gear train 660 includes planetary gears 664 supported by a carrier662, which is connected to the inner shaft 640 that supports the lowpressure turbine 646. A sun gear 666 is centrally arranged relative toand intermeshes with the planetary gears 664. A ring gear 670circumscribes and intermeshes with the planetary gears 664. In theexample, a fan shaft 672 is connected to the fan 642. The low pressurecompressor 644 is supported by a low pressure compressor rotor 668,which is rotationally fixed relative to the ring gear 670 in theexample.

The carrier 662 is rotationally driven by the low pressure turbine 646through the inner shaft 640. The planetary gears 664 provide thedifferential input to the fan shaft 672 and low pressure compressorrotor 668 based upon the geometry ratio. The geared architecture 648includes an additional speed change device 674 interconnecting the innershaft 640 and the gear train 660. The speed change device 674 receivesrotational input from the sun gear 666 and couples the fan shaft 672 tothe gear train 660, which enables slower fan speeds.

The inducer 676 is arranged in the core flow path C to provide someinitial compression to the air before entering the low pressurecompressor section 644. The inducer 676 is fixed to the sun gear 666 forrotation at the same rotational speed.

In the arrangements shown in FIGS. 2-8, the relative rotationaldirections are shown for each of the fan, low pressure compressorsection, high pressure compressor section, high pressure turbinesection, low pressure turbine section and inducer. The gearedarchitectures may be configured in a manner to provide the desiredrotational direction for a given engine design.

The example geared architectures enable large fan diameters relative toturbine diameters, moderate low pressure turbine to fan speed ratios,moderate low pressure compressor to low pressure turbine speed ratios,high low pressure compressor to fan speed ratios and compact turbinesection volumes. The low pressure turbine section may include betweenthree and six stages, for example.

The rotational speeds of the sun gear, ring gear and carrier aredetermined by the geometry ratio of the differential gear train. Theinterrelationship of these components can be expressed using thefollowing equation:

$\begin{matrix}{{\frac{X_{carrier}}{X_{ring}} = \frac{GR}{1 + {GR}}},{where}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

X_(carrier) is the nomograph distance of the planetary rotational axisfrom the sun gear axis,

X_(ring) is the nomograph radius of the ring gear, and

GR is the geometry ratio.

Thus, for a geometry ratio of 3.0,

$\frac{X_{carrier}}{X_{ring}} = {0.75.}$

The relative sizes amongst the sun gear, planetary gears and ring gearfor several different geometry ratios are schematically depicted inFIGS. 9A-9C. Referring to FIG. 9A, the epicyclic gear train 760 includesa sun gear 766, planetary 764, carrier 762 and ring gear 770 that aresized to provide a geometry ratio of 3.0. Referring to FIG. 9B, theepicyclic gear train 860 includes a sun gear 866, planetary 864, carrier862 and ring gear 870 that are sized to provide a geometry ratio of 2.0.Referring to FIG. 9C, the epicyclic gear train 960 includes a sun gear966, planetary 964, carrier 962 and ring gear 970 that are sized toprovide a geometry ratio of 1.5. In the examples, the ring gear radiusremains constant.

FIG. 10 graphically depicts effects of the geometry ratio on therotational speeds and directions of the sun and ring gears and thecarrier. The upper, lighter shaded bars relate to FIG. 9A-9C. Assuming arotational input from the low pressure turbine to the carrier of 10,000RPM, the sun gear would be driven at 15,000 RPM and the ring gear wouldbe driven at 8,333 RPM for a geometry ratio of 3.0. In an arrangement inwhich the fan is coupled to the ring gear and the sun gear is coupled tothe low pressure compressor, like the arrangement shown in FIG. 2, thefollowing speed ratios would be provided: LPT:fan=1.2, LPC:LPT=1.5, andLPC:fan=1.8.

The lower, darker shaded bars relate to FIGS. 11A-11C. The carrier andring gear rotate in the opposite direction than depicted in FIG. 9A-9C.

Although an example embodiment has been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of the claims. For that reason, the following claimsshould be studied to determine their true scope and content.

What is claimed is:
 1. A gas turbine engine comprising: first and secondshafts rotatable about a common axis; a first turbine section supportedon the first shaft; second compressor and turbine sections supported onthe second shaft; a fan; a first compressor section arranged in an axialflow relationship with the second compressor and the first and secondturbines; a geared architecture operatively connecting the first shaftand the fan, wherein the geared architecture includes first and secondgear trains, the first gear train an epicyclic gear train, and thesecond gear train configured to provide a speed reduction; and aninducer downstream from the fan and operatively coupled to the geartrain, wherein the inducer is coupled to the first gear train, theepicyclic gear train is a differential gear train that includes a sungear, planetary gears arranged about and intermeshing with the sun gear,and a ring gear circumscribing and intermeshing with the planetarygears, wherein the inducer is rotationally fixed relative to the ringgear.
 2. The gas turbine engine according to claim 1, comprising abypass flow path and a core flow path, the first and second compressorand turbine sections arranged in the core flow path, and the fanextending into the bypass flow path, the inducer arranged in the coreflow path outside of the bypass flow path and upstream from the firstcompressor section.
 3. The gas turbine engine according to claim 2,wherein first and second shafts respectively provide low and highspools, and the first compressor and turbine sections are low pressurecompressor and turbine sections, and the second compressor and turbinesections are high pressure compressor and turbine sections.
 4. A gasturbine engine comprising: first and second shafts rotatable about acommon axis; a first turbine section supported on the first shaft;second compressor and turbine sections supported on the second shaft; afan; a first compressor section arranged in an axial flow relationshipwith the second compressor and the first and second turbines; a gearedarchitecture operatively connecting the first shaft and the fan, whereinthe geared architecture includes first and second gear trains, the firstgear train an epicyclic gear train, and the second gear train configuredto provide a speed reduction to the first gear train; and an inducercoupled to the second gear train, wherein the inducer is configured torotate at a different rotational speed than the fan.
 5. The gas turbineengine according to claim 4, wherein the inducer is rotationally fixedrelative to the fan.
 6. The gas turbine engine according to claim 4,wherein the inducer is configured to rotate at a different rotationalspeed than the first compressor section.
 7. The gas turbine engineaccording to claim 6, wherein the inducer is configured to rotate at adifferent rotational speed than the fan.